Constant Scallop Height Tool Paths Research Articles

Collisionless tool orientation smoothing above blade stream surface using NURBS envelope

In five-axis machining, tool orientation above a blade stream surface may lead to tool collision and a decrease in workpiece rigidity. Hence, collisionless tool orientation smoothing (TOS) becomes an important issue. On the basis of a constant scallop height tool path, the triangular facets in the faces, vertices format are constructed from cutter contact (CC) using the Voronoi incremental algorithm. The cutter location (CL) points candidate set is represented by an oblique elliptic cone whose vertex lies at CC using NURBS envelope. Whether the CL point is above its CC is judged by the dot product between the normal vector and the point on triangulation nearest to the CL point. The curvatures at CC are obtained by fitting a moving least square (MLS) quadratic patch to the local neighborhood of a vertex and calculating eigenvectors and eigenvalues of the Hessian matrix. Triangular surface elastic energy is employed as the weight in selection from the NURBS envelope. The collision is judged by NURBS surface intersection. TOS can then be expressed by selecting a CL point for each CC point and converted into a numerical control (NC) code automatically according to the postprocessor type of the machine center. The proposed method is verified by finishing of a cryogenic turboexpander impeller of air separation equipment.

Iso-Scallop Toolpath Generation for Orthogonal Turn-Milling of Ruled Surfaces

This paper presents a new method of computing constant scallop height tool paths for orthogonal turn-milling of ruled surfaces. Indeed, the traditional tool path generation method in orthogonal turn-milling leads to unevenly distributed scallop-height between adjacent toolpaths, which prevent from reaching the required quality. The proposed approach is adequate for orthogonal mill-turning whose toolpath topology is parallel-pattern or spiral-pattern and the constant scallop height is guaranteed by modifying the path-interval distance through adjustment of the offset distance.The machining results obtained show that this method can reduce uneven distribution of scallop height.

A New Constant Scallop-Height Smooth Tool-Path Planning Algorithm

A new constant scallop-height smooth tool-path planning algorithm is presented in this paper. The algorithm can generate smooth tool path by controlling the curvature of the tool path so as to avoid the tool path’s inflexion which is often generated in traditional constant scallop height tool path planning affecting the machining surface quality. Taking a parametric surface for example, the algorithm is programmed using Matlab software and compared with the traditional one, the result shows that this algorithm can acquire the minimum curvature radius of tool-path line and improve machining quality. Especially in high speed milling, the idea of algorithm has obvious merits in practice. The paper ends with some recent patents and further developments in the fields. A method for calculating depth of cut without any milling selfexcited vibration, a system produces orthodontic aligners by CNC machining and etc.

Constant scallop-height tool path generation for three-axis discrete data points machining

This paper presents a new approach for the determination of constant scallop-height tool paths in the machining of discrete data points using three-axis ball-end milling. Compared with the existing approaches for surfaces, this approach avoids offsetting data points, which is complex and time consuming. This paper firstly creates the local coordinate system centered at each CL point of the current path to calculate the corresponding scallop point and then the similar local coordinate system is created at each scallop point to calculate the wanted CL point of the next tool path. The tool paths generated by the approach keep the scallop-height constant and meet the step error requirement. The experiment result indicates that the approach is feasible and efficient and the overall tool path length can be reduced significantly compared with the iso-planar method.

High precision tool path planning algorithm for complex parametric surface

A high precision tool path planning algorithm with error compensation for complex parametric surfaces——high precision tool path planning algorithm of error compensation (HPTPPACPS) is proposed based on studying the constant scallop-height tool path planning for parametric surface. Based on analyzing the relationship of cutter contact point, its corresponding primary and fine cutter location points of adjacent tool path, error compensation is introduced to improve the precision of the fine cutter location point. The reasonably simplified expression of error compensation is presented in addition to the expressions of distance error of theoretical cutter location point, its corresponding primary and fine cutter location points. The calculated precision of the parameter value of the cutter location of adjacent tool path corresponding to cutter contact point is increased greatly, which leads to a high processing precision of complex parametric surface, by HPTPPACPS with error compensation on the condition that the real-time performance is satisfied. The adaptability of HPTPPACPS to machine complex parametric surfaces in high precision is proved by the result of simulation example with flat bottom milling-tool.

A CL surface deformation approach for constant scallop height tool path generation from triangular mesh

In this paper, we present a cutter location (CL) surface deformation approach for constant scallop height tool path generation from triangular mesh. The triangular mesh model of the stereo lithography (STL) format is offset to the CL surface and then deformed in accordance with the deformation vectors, which are computed by the slope and the curvature of the CL surface. In addition, the tool path, which is computed by slicing the deformed CL surface, is inversely deformed by those same deformation vectors to a tool path with a constant scallop height. The proposed method is implemented, and a tool path is generated and tested by simulation and by numerical control (NC) machining. The scallop height was found to be constant over the entire machined surface, demonstrating much better quality than that of mesh slicing, under the same constraints for machining time.

Iso-scallop tool path generation in 5-axis milling

This paper presents a new method of computing constant scallop height tool paths in 5-axis milling on sculptured surfaces. Usually, iso-scallop tool path computation methods are based on approximations. The attempted scallop height is modelled in a given plane to ensure a fast computation of the tool path. We propose a different approach, based on the concept of the machining surface, which ensures a more accurate computation. The machining surface defines the tool path as a surface, which applies in 3- or 5-axis milling with the cutting tools usually used. The machining surface defines a bi-parametric modelling of the locus of a particular point of the tool, and the iso-scallop surface allows to easily find iso-scallop tool centre locations. An implementation of the algorithms is done on a free-form surface with a filleted end mill in 5-axis milling.

Efficient five-axis machining of free-form surfaces with constant scallop height tool paths

Generation of efficient tool paths is essential for the cost-effective machining of parts with complex free-form surfaces. A new method to generate constant scallop height tool paths for the efficient five-axis machining of free-form surfaces using flat-end mills is presented. The tool orientations along the tool paths are optimized to maximize material removal and avoid local gouging. The distances between adjacent tool paths are further optimized according to the specified scallop height constraint to maximize machining efficiency. The constant scallop height tool paths are generated successively across the design surface from the immediate previous tool path and its corresponding scallop curve. The scallop surface, an offset surface of the three-dimensional design surface based on the specified scallop height, is used to establish accurately the scallop curve with the constant scallop height. The present method was implemented and validated through the five-axis machining of a typical free-form surface. The results showed that the conventional isoparametric tool paths were over 36% longer in the total tool path length and less efficient than the constant scallop height tool paths generated by the present method.

MULTI-POINT MACHINING WITH ANTI-GOUGING AND SCALLOP HEIGHT CONTROL

Multi-Point Machining (MPM) is a tool positioning strategy for 5-axis machining of complex surfaces. A multi-point tool position results in tangential contact between the tool and the design surface at several points. By machining at several points on the tool simultaneously, material removal rates can be improved. In this paper several issues regarding multi-point machining are resolved. First, a much faster method for solving the equations governing multi-point contact is presented. Second, a method of estimating scallop height is described. This estimator makes it possible to produce constant scallop height tool paths. Finally a method of eliminating interference between the tool and the surface has been developed and integrated into the MPM tool positioning strategy.

Constant scallop-height tool path generation for three-axis sculptured surface machining

This paper presents a new approach for the determination of efficient tool paths in the machining of sculptured surfaces using 3-axis ball-end milling. The objective is to keep the scallop height constant across the machined surface such that redundant tool paths are minimized. Unlike most previous studies on constant scallop-height machining, the present work determines the tool paths without resorting to the approximated 2D representations of the 3D cutting geometry. Two offset surfaces of the design surface, the scallop surface and the tool center surface, are employed to successively establish scallop curves on the scallop surface and cutter location tool paths for the design surface. The effectiveness of the present approach is demonstrated through the machining of a typical sculptured surface. The results indicate that constant scallop-height machining achieves the specified machining accuracy with fewer and shorter tool paths than the existing tool path generation approaches.

A Surface Based Approach for Constant Scallop HeightTool-Path Generation

The machining of sculptured surfaces like molds and dies in 3-axis milling relies on the chordal deviation, the scallop height parameter and the planning strategy. The choice of these parameters must ensure that manufacturing surfaces respect the geometrical specifications. The current strategies of machining primarily consist in driving the tool according to parallel planes which generates a tightening of the tool paths and over quality. The constant scallop height planning strategy has been developed to avoid this tightening. In this paper, we present a new method of constant scallop height tool path generation based on the concept of the machining surface. The concept of the machining surface is exposed and its use to generate constant scallop height tool paths. The approach is confronted with existing methods in terms of precision and in particular its aptitude to treat curvature discontinuities.